All thermosyphon solar heating collector panels and radiative or evaporative cooling panels absorb thermal energy from the sun or coolness from the surrounding environment. Absorbing thermal energy from the sun or coolness from the surrounding environment establish a thermosyphon convection current flow in the panel's heating and/or cooling tubes that usually moves the heated or cooled fluid respectively into one or more storage tanks. Some of this energy exchange between the panel's heating and/or cooling tubes and the surrounding environment either heats or cools fluid in the panel's tubes. However, a significant portion of energy from this exchange is transferred into kinetic energy of the thermosyphonic flows induced in the fluid inside the panel's heating and/or cooling tubes.
U.S. Pat. No. 6,014,968 entitled “Tubular Heating-Pipe Solar Water-Heating-System With Integral Tank” that issued Jan. 18, 2000, on a patent application filed in the name of Siang Teik Teoh (“the '968 patent”) discloses a solar water-heating system having collector core that includes a plurality of hollow heating-pipes. Each heating-pipe has a longitudinal axis and an interior that is surrounded by an outer wall. When assembled into the collector core of the solar water-heating system, the heating-pipes are aligned substantially parallel to each other, and in use are adapted to be inclined to the horizontal. Thus, when in use each of the heating-pipes has an open upper end that is elevated above the heating-pipe's closed lower end. The open upper end of the heating-pipes disclosed in the '968 patent extend directly to, open into, and communicate directly with:                1. a lower level of a hot-water storage-tank; or        2. a lower portion of another the solar water-heating-panel.        
Each of the hollow heating-pipes has an outer wall that surrounds a hollow cooler-water return-pipe. The cooler-water return-pipe within each of the heating-pipes has an internal cross-sectional area that is approximately equal to one-third (⅓) to one-half (½) of an internal cross-sectional area enclosed by the surrounding heating-pipe's outer wall. The cooler-water return-pipe within each of the heating-pipes also has a length that is slightly longer than a length of the outer wall of the heating-pipe. Thus, the open upper end of the cooler-water return-pipe extends beyond the open upper end of the heating-pipe's outer wall. In this way the upper end of the cooler-water return-pipe extends into and communicates directly with:                1. the lower level of a hot-water storage-tank; or        2. the lower portion of another the solar water-heating-panel.A lower end of each cooler-water return-pipe is perforated so fluid may flow outward from within the lower end of each cooler-water return-pipe toward the surrounding outer wall of the heating-pipe.        
Preferably, the solar water-heating system disclosed in the '968 patent includes a transparent cover, usually made of glass, that is disposed immediately adjacent to and shields the heating-pipes. The solar water-heating system disclosed in the '968 patent when assembled with evacuated glass thermosyphon coaxial heating tubes exhibits the highest thermal efficiencies of all presently known solar water-heating systems.
Similarly, U.S. Pat. No. 7,398,779 entitled “Thermosiphoning System With Side Mounted Storage Tanks” (“the '779 patent”) also discloses a single layer collector panel. However, the collector panel disclosed in the '779 patent dissipates kinetic energy (momentum) present in fluid rising and/or falling through the panel's tubes when the rising and/or falling flows meets an upper or lower header manifold tank which stops the rising or falling flow.
Patent Cooperation Treaty (“PCT”) International Patent Application no. 2010/003046 that was published 26 May 2011, as International Publication no. WO 2011/062649 for a patent application filed in the name of Siang Teik Tech, et al. entitled “Coaxial Tube Solar Heater With Nighttime Cooling” (“the PCT Patent Application”) discloses a solar heating-and-cooling system that includes a collector array panel having a single layer of coaxial thermosyphon heating/cooling-tubes. In one embodiment, each of the thermosyphon heating/cooling-tubes included in the collector-array-panel connects:                1. at an upper end to an upper manifold; and        2. at a lower end to an intermediate manifold.A heated-liquid coaxial tube connects the upper manifold upward to a hot-water storage-tank, and a cool-liquid coaxial tube connects the intermediate manifold downward to a cold-water storage-tank. The heated-liquid cool-liquid coaxial tube and the cool-liquid coaxial tube respectively carry hot and cold water between the collector-array-panel and the hot water and cold water storage tanks.        
In general, single layer solar water-heating system such as that disclosed in the '968 and '779 Patents and a single layer solar heating-and-cooling system such as that disclosed in the PCT Patent Application exhibit stagnation. That is, the thermosyphonic flow stops during marginal solar radiation conditions such as at sunrise or sunset. Consequently, there exists a need for a solar heating and/or cooling system which betters thermosyphonic flow during marginal solar conditions.